1. Field of the Invention
The present invention relates to a method for identifying optical disks suitable for the case of using plural kinds of optical disks having physical specifications identical to each other, a method for reproducing optical disks, and an optical disk apparatus.
2. Description of the Related Art
In recent years, as technology relating to optical disks progresses, there have been suggested optical disks having physical specifications identical to each other, and having contents of recorded signals different from each other. For example, as a compact disk, on top of a CD-DA in which music data is recorded, also suggested are disks such as a CD-ROM in which computer data and the like is recorded, and a video CD (i.e. a compact disk) in which images (i.e. video images), sounds, and the like are recorded. In addition, as an optical disk called as a digital versatile disk (DVD) which has a high recording capacity attained by giving a recording density higher than that of a compact disk, suggested are a DVD-ROM in which computer data is recorded, a DVD-Video in which images and sounds of movies are recorded, and the like.
A CD-ROM is constituted by giving a CD-DA an ability of recording an error correction code into the data zone of the sector, and by use of the error correction data, the CD-ROM has an increased ability of error correction as compared with the CD-DA. In this structure, when a CD-ROM decoding circuit for performing error correction using the above-described error correction code is provided to a disk reproducing apparatus for obtaining a reproduction output signal by reading a signal recorded in the CD-DA and then by demodulating the read signal, both the CD-DA and the CD-ROM can be reproduced in a single disk reproducing apparatus. The video CD records video and audio data compressed in compliance with the Moving Picture Experts Group (MPEG) 1 standards, by use of a physical format of the CD-ROM XA which has been established by expanding the CD-ROM standards. In this structure, when an MPEG decoder circuit for decoding the compressed data is further provided to the disk reproducing apparatus, not only a CD-CA and a CD-ROM but also a video CD can be reproduced in a single disk reproducing apparatus.
In a disk reproducing apparatus for reproducing a DVD disk similarly, when an MPEG decoder circuit for decoding video and audio data compressed in compliance with the Moving Picture Experts Group (MPEG) 2 standards is provided to a DVD-ROM disk reproducing apparatus for obtaining a reproduction output signal by reading a signal recorded in the disk and then by performing demodulation and error correction for the signal, not only a DVD-ROM disk but also a DVD-Video disk can be reproduced in a single disk reproducing apparatus.
In the above-described optical disks, in the cases where the optical disks themselves have defects, where scratches are created on the optical disks, or where dusts are attached on the optical disks, possibilities arise that the data recorded therein may not be read correctly, due to the influences of the defects, scratches, dusts, and the like. If such troubles occur in the case where the recorded data is computer data, it is desirable to repeat retry where the recorded data is read again, so as to obtain data as correct as possible. However, if the recorded data is video data or audio data, and the retry is repeated in an attempt to obtain correct data, the period in which the data is not read become longer, resulting in discontinuity of the images and sounds.
In such situations, the present invention provides a method for identifying optical disks in which the kind of data recorded in each of the optical disks is identified and a reproducing operation is performed in accordance with each of the optical disks, a method for reproducing optical disks, and an optical disk apparatus.